foreach my $dc ( %{ $re->directoryCategory() } ) {

Uh, you haven't just forgotten:

foreach my $dc (keys %{ $re->directoryCategory() } ) {

Update:
Check with ref() and reftype() that it really is a hash... :-)

This works for me:
perl -e '$a={1,2,3,4}; bless $a,"foo"; print "$_\n" foreach (keys %$a);'